Automatic speed changer controller, automatic speed changer control method, and recording medium having program for method recorded thereon

ABSTRACT

An automatic transmission control apparatus includes a continuously variable transmission (CVT) which, in turn, includes a primary pulley, a secondary pulley, a belt stretched between the primary pulley and the secondary pulley. The control apparatus further includes a pinching pressure generator for generating a pinching pressure on the belt, a travel environment all detector for detecting the travel environment of a vehicle, a torque variation estimator for estimating the transmission torque variation during travel, and a pinching pressure changer for changing the pinching pressure based on the estimation. The pinching pressure is prevented from constantly increasing because the transmission torque variation during travel is estimated, and the pinching pressure for the belt is changed based on the estimation. Accordingly, the torque transmission efficiency can be increased, and the fuel efficiency can thus be improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Application (35 USC 371) ofPCT/JP00/09136 and claims priority of Japanese Application No. 11-367656filed Dec. 24, 1999 and of Japanese Application No. 2000-389902 filedDec. 22, 2000.

TECHNICAL FIELD

The present invention relates to an automatic transmission controlapparatus, an automatic transmission control method and a recordingmedium with a program for the method recorded thereon.

BACKGROUND ART

Conventionally, in a vehicle equipped with an automatic transmission,the rotation generated by the engine is transmitted to a transmissionmechanism, in which gear shifting is performed, and the rotation afterthe gear shifting is transmitted to a drive wheel to make the vehicletravel.

Automatic transmissions include standard (discontinuously variable)transmissions and continuously variable transmissions. In a standarddiscontinuously variable transmission, the gear ratio of thetransmission mechanism is changed by changing the combination of a gearelement for inputting rotation to a planetary gear unit and a gearelement for outputting rotation from the planetary gear unit or thelike. In the continuously variable transmission, a belt is stretchedbetween a primary pulley and a secondary pulley so that the gear ratioof the transmission mechanism is continuously changed by changing theradial position of the belt on the primary and the secondary pulley,namely, changing the effective diameter of the pulleys. Consequently,the primary pulley and the secondary pulley are provided with a fixedsheave and a movable sheave, respectively, and the effective diameter ofeach is changed by axially shifting each movable sheave by a drivingmeans as a hydraulic servo, an electric motor or the like.

In the continuously variable transmission, when the belt pinchingpressure is high, torque transmission efficiency becomes low. While thebelt pinching might be lowered, when the belt pinching pressure islowered the torque transmitted in the continuously variable transmissionmay vary over a larger range than suitable when the vehicle encountersbumps on a rough road, or when the accelerator pedal is depressedsuddenly. As a result slippage occurs between the primary pulley or thesecondary pulley and the belt, and the primary pulley, the secondarypulley and the belt wear to remarkably lower the service life of thecontinuously variable transmission.

Therefore, the pinching pressure is increased by a certain allowance toprevent slippage from occurring. Where the allowance is m, and thetorque to be input to the continuously variable transmission or inputtorque is T₁, the allowance m is set to:

M=(a−1)×T ₁

Wherein a is a constant, and the constant a is determined, for example,to be 1.04.

A continuously variable transmission in which the allowance m can bechanged according to the driving state, driven state or the like of anengine has been disclosed in Japanese Patent Publication No. HEI6-288448.

In the aforementioned conventional continuously variable transmission,as the pinching pressure is always higher by the allowance m, the torquetransmission efficiency is lowered accordingly.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an automatictransmission control apparatus, an automatic transmission controlmethod, and a recording medium with a program for the method recordedthereon, which solve the problems of the conventional continuouslyvariable transmission, which improve durability of a continuouslyvariable transmission, and which increase the torque transmissionefficiency.

Accordingly, the present invention provides an automatic transmissioncontrol apparatus which includes a primary pulley, a secondary pulley, abelt stretched between the primary pulley and the secondary pulley,pinching pressure generation means for generating a belt pinchingpressure, travel environment detection means for detecting a travelenvironment of a vehicle, torque variation estimation processing meansfor estimating the transmission torque variation during travel, andpinching pressure change processing means for changing the pinchingpressure based on the estimated results.

In this case, since the transmission torque variation during travel isestimated and the belt pinching pressure is changed based on theestimation, the pinching pressure is prevented from constantlyincreasing. Accordingly, torque transmission efficiency can be increasedand fuel consumption can be improved.

Since the pinching pressure is regulated to correspond to the travelenvironment, slippage is prevented from occurring between the primarypulley or the secondary pulley and the belt. Consequently, the primarypulley, the secondary pulley and the belt are prevented from wearing andthe durability of the continuously variable transmission is therebyimproved.

In a preferred embodiment of the automatic transmission controlapparatus of the invention, the pinching pressure change processingmeans increases the belt pinching pressure when the transmission torquetends to vary greatly and lowers the belt pinching pressure when thetransmission torque hardly varies.

The torque variation estimation processing means may estimate thetransmission torque variation based on the change of a shift scheduleselected based on the travel environment or based on the travel area.

The torque variation estimation processing means may estimate that thetransmission torque hardly varies in a travel environment for which itis estimated that a sudden change of throttle opening will not occur,e.g., a congested road, a downhill road, or an expressway.

In a preferred embodiment of the automatic transmission controlapparatus of the invention, furthermore, the travel environment includesat least a travel area and the driving state. The torque variationestimation processing means estimates the transmission torque variationbased on at least either the travel area or the driving state.

In one embodiment of the automatic transmission control apparatus of theinvention, the torque variation estimation processing means estimatesthat the transmission torque will tend to vary easily in a travelenvironment where it is estimated that the throttle will be open amedium to high degree and the accelerator will be turned on and offfrequently.

The travel environment where it is estimated that the throttle will beopen a medium to high degree and the accelerator will be turned on andoff frequently may be, for example, a mountain road or an uphill grade.

In another preferred embodiment of the automatic transmission controlapparatus of the invention, the torque variation estimation processingmeans estimates that the transmission torque will hardly vary in atravel environment where it is estimated that there is a smallpossibility of sudden acceleration, for example, where there is novehicle ahead during travel on an expressway and where there is avehicle ahead during a stop.

In still another preferred embodiment automatic transmission controlapparatus of the invention, the torque variation estimation processingmeans estimates that the transmission torque will tend to vary easily ina travel environment where it is estimated that there is a largepossibility of sudden acceleration, for example, where there is avehicle ahead during travel on an expressway.

Preferably, the travel environment includes at least a road surfacecondition and the torque variation estimation processing means estimatesthe transmission torque variation based on the road surface condition.

In another embodiment of the automatic transmission control apparatus ofthe invention, the torque variation estimation processing meansestimates that the transmission torque will tend to vary easily in atravel environment where it is estimated that the reaction forcereceived from the road surface will be large, for example, where theroad surface is a gravel road surface or an ice and snow-covered roadsurface.

Preferably, the torque variation estimation processing means estimatesthat the transmission torque will hardly vary in a travel environmentwhere it is estimated that the reaction force received from the roadsurface will be small, e.g., a smoothly frozen road surface.

In still another embodiment of the automatic transmission controlapparatus of the invention, the travel environment detection meansdetects the travel environment based on operation information.

The control method of the present invention comprises the steps ofdetecting travel environment of the vehicle, estimating the transmissiontorque variation during travel based on the detected travel environment,and changing the belt pinching pressure based on the results of theestimation.

The present invention also provides a machine readable medium having,encoded thereon, a program for the automatic transmission control methodwhich detects a travel environment of the vehicle, estimates thetransmission torque variation during travel based on the detected travelenvironment, and changes the belt pinching pressure based on the resultsof the estimation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an automatic transmission control apparatusin a first embodiment of the invention.

FIG. 2 is a schematic diagram of a continuously variable transmission inthe first embodiment of the invention.

FIG. 3 is a more detailed block diagram of the automatic transmissioncontrol apparatus in the first embodiment of the invention.

FIG. 4 is a main flowchart of the routine for operation of the automatictransmission control apparatus in the first embodiment of the invention.

FIG. 5 is a gear shifting diagram referred to in a normal controlroutine in the first embodiment of the invention.

FIG. 6 is a first gear shifting diagram referred to in an adaptivecontrol routine in the first embodiment of the invention.

FIG. 7 is a second gear shifting diagram referred to in the adaptivecontrol routine in the first embodiment of the invention.

FIG. 8 is a third gear shifting diagram referred to in the adaptivecontrol routine in the first embodiment of the invention.

FIG. 9 is a fourth gear shifting diagram referred to in an adaptivecontrol routine in the first embodiment of the invention.

FIG. 10 shows a subroutine for allowance correction in the firstembodiment of the invention.

FIG. 11 shows a correction value table used in the first embodiment ofthe invention.

FIG. 12 is a main flowchart of a routine for operation of an automatictransmission control apparatus in a second embodiment of the invention.

FIG. 13 shows a subroutine for allowance correction in the secondembodiment of the invention.

FIG. 14 shows a correction value table used in the second embodiment ofthe invention.

FIG. 15 shows a subroutine for allowance correction in a thirdembodiment of the invention.

FIG. 16 shows a correction value table used in the third embodiment ofthe invention.

FIG. 17 shows a subroutine for allowance correction processing in afourth embodiment of the invention.

FIG. 18 shows a correction value table used in the fourth embodiment ofthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, preferred embodiments of the present invention will be described indetail by referring to the drawings. Here, a continuously variabletransmission will be described.

FIG. 1 shows a primary pulley 126, a secondary pulley 131, a belt 132stretched between the primary pulley 126 and secondary pulley 131, ahydraulic servo 135 as pinching pressure generation means for generatingpinching pressure for the belt 132, travel environment detection means91 for detecting the travel environment of a vehicle, torque variationestimation processing means 93 for estimating transmission torquevariation during travel, based on the detected travel environment, andpinching pressure change processing means 93 for changing the pinchingpressure based on the results of the estimation.

As shown in FIG. 2, a continuously variable transmission 10 comprises abelt type transmission mechanism 102, a forward/reverse movementswitching apparatus 103, a torque converter 106 with a built-in lockupclutch 105, a counter shaft 107 and a differential apparatus 109.

The torque converter 106 comprises a pump impeller 111 coupled with anoutput shaft 110 of an engine (not shown) via a front cover 117, aturbine runner 113 coupled with an input shaft 112 via a lockup clutchplate 104 and a damper spring 120, and a stator 116 supported through aone-way clutch 115. The lockup clutch 105 is disposed between the inputshaft 112 and the front cover 117. An oil pump 121 is coupled with anddriven by the pump impeller 111.

The transmission mechanism 102 comprises the primary pulley 126, thesecondary pulley 131 and the metallic belt 132 stretched between theprimary pulley 126 and the secondary pulley 131. The primary pulley 126comprises a fixed sheave 123 fixed to a primary shaft 122, and a movablesheave 125 slidably supported for sliding movement along the axis of theprimary shaft 122. The secondary pulley 131 comprises a fixed sheave 129fixed to a secondary shaft 127, and a movable sheave 130 slidablysupported for sliding movement along the axis of the secondary shaft127.

A hydraulic servo 133 serves as a first driving means and has a doublepiston disposed at the back of the movable sheave 125. A hydraulic servo135 serves as a second driving means or “pinching pressure generationmeans” and has a single piston disposed at the back of the movablesheave 130.

The hydraulic servo 133 comprises a cylinder member 136 and a reactionforce support member 137 fixed to the primary shaft 122, and acylindrical member 139 and a piston member 140 fixed to the back of themovable sheave 125. A first oil chamber 141 is formed by the cylindricalmember 139, reaction force support member 137 and back surface of themovable sheave 125. A second oil chamber 142 is formed by the cylindermember 136 and the piston member 140.

The first and second oil chambers 141, 142 communicate with each othervia a communication hole 137 a, so that the hydraulic servo 133 issupplied with the same hydraulic pressure as the hydraulic servo 135.Therefore, the axial force generated by the hydraulic servo 133 isapproximately twice the axial force generated by the hydraulic servo135.

The hydraulic servo 135 comprises a reaction force support member 143fixed to the secondary shaft 127 and a cylindrical member 145 fixed tothe back of the movable sheave 130. The reaction force support member143, the cylindrical member 145 and the back surface of the movablesheave 130 define one oil chamber 146, and a preload spring is disposedbetween the movable sheave 130 and the reaction force support member143.

The forward/reverse movement switching apparatus 103 comprises a doublepinion planetary gear unit 150, a reverse brake B and a direct clutch C.In the double pinion planetary gear unit 150, a sun gear S and the inputshaft 122 are coupled to each other, a carrier CR supporting first andsecond pinions P1, P2 and the fixed sheave 123 are coupled to eachother, a ring gear R and the reverse brake B are coupled to each other,and the carrier CR and the ring gear R are coupled via the direct clutchC.

A large gear 151 and a small gear 152 are fixed to the counter shaft107. The large gear 151 meshes with a gear 153 fixed to the secondaryshaft 127, and the small gear 152 meshes with a gear 155 fixed to adifferential case 166 of a differential apparatus 109. In thedifferential apparatus 109, revolution of a differential gear 156supported by the differential case 166 is transmitted to right and leftwheel shafts 160, 161 through right and left side gears 157, 159.

Also, a number of projected/recessed portions 123 a are formed at equalintervals by gear cutting on the outer periphery of the fixed sheave123, and a primary pulley revolution speed sensor 162 comprising anelectromagnetic sensor fixed to a case (not shown) is disposed so as toface the projected/recessed portions 123 a. A number ofprojected/recessed portions 129 a are formed at equal intervals by gearcutting on the outer periphery of the fixed sheave 129, and a secondarypulley revolution speed sensor, that is, a vehicle speed sensor 44comprising an electromagnetic sensor fixed to the case is arrangedfronting the projected/recessed portions 129 a. Accordingly, the vehiclespeed V representing a vehicle travel condition can be detected by thevehicle speed sensor 44, while the input pulley revolution speed can bedetected by the primary pulley revolution speed sensor 162.

Moreover, an engine speed sensor 165 comprising an electromagneticsensor fixed to the case is arranged in the proximity of the front cover117, and the engine speed sensor 165 can detect the engine speed N_(E)representing an engine load.

In the above-described continuously variable transmission 10 therotation output by the engine is transmitted to the transmissionmechanism 102 via the torque converter 106 and the forward/ reversemovement switching apparatus 103, and after a gear shift by thetransmission mechanism 102, is further transmitted to the differentialapparatus 109 via the gear 153, the large gear 151, the small gear 152and the gear 155. Then, in the forward/reverse switching apparatus 103,when the direct clutch C is engaged with the reverse brake B released,the double pinion planetary gear 150 is put in a directly connectedstate, so that the rotation transmitted to the input shaft 112 istransmitted as is to the primary pulley 126, and thus the vehicle ismoved forward. On the other hand, when the direct clutch C is releasedwith the reverse brake B engaged, the rotation transmitted to the inputshaft 112 is reversed and transmitted to the primary pulley 126, thusthe vehicle is moved backward.

The hydraulic servo 133 is used to change the effective diameters of theprimary pulley 126 and the secondary pulley 131. That is, in the case ofperforming an up-shift, the hydraulic servo 133 is drained, so that theeffective diameter of the primary pulley 126 is enlarged while theeffective diameter of the secondary pulley 131 is reduced. As a result,the gear ratio is reduced. In case of a down-shift, hydraulic pressureis supplied to the hydraulic servo 133, the effective diameter of theprimary pulley 126 is enlarged, while the effective diameter of thesecondary pulley 131 is reduced and, as a result, the gear ratio isincreased.

The hydraulic servo 135 is used to apply and change the pinchingpressure for the belt 132. That is, when the hydraulic servo 135 issupplied with hydraulic pressure, a pinching pressure corresponding tothe hydraulic pressure is generated, and the secondary pulley 131pinches the belt 132 with the generated pinching pressure between thefixed sheave 129 and the movable sheave 130.

Moreover, first and second hydraulic pressure control valves (not shown)are disposed in the hydraulic pressure circuit, and the hydraulic servos133, 135 are supplied with hydraulic pressure as regulated by the firstand second hydraulic pressure control valves, respectively. A solenoidsignal generated by the automatic transmission control section describedbelow is sent to the solenoids of the first and second hydraulicpressure control valves.

In this embodiment, the hydraulic servo 133 is used to change theeffective diameters of the primary pulley 126 and the secondary pulley131, and the hydraulic servo 135 is used to apply and change thepinching pressure on the belt 132. However, the hydraulic servo 135 maybe used to change the effective diameters of the primary pulley 126 andthe secondary pulley 131, and the hydraulic servo 133 may be used toapply and change the pinching pressure on the belt 132.

Although the hydraulic servos 133, 135 are used as the first and seconddrive means in this embodiment, one or both of the hydraulic servo 133and the hydraulic servo 135 can be substituted by an electric motor. Inthis case, at least one of movable sheaves 125 and 130 is forced toshift in the axial direction by driving the electric motor, so theeffective diameters of the primary pulley 126 and the secondary pulley131 can be changed by adjusting the position of the movable sheave 125,while the pinching pressure on the belt 132 can be changed by adjustingthe position of the movable sheave 130.

The automatic transmission control apparatus will now be described withreference to FIG. 3.

FIG. 3 shows an automatic transmission control section 40 forcontrolling the entire continuously variable transmission 10 (FIG. 2),an engine control section 13 for controlling the entire engine (notshown), and a navigation apparatus 14.

FIG. 3 further shows a vehicle/driver operation information detectionsection 40, and the vehicle/driver operation information detectionsection 40 comprises a steering sensor 24, a turn signal sensor 41, anaccelerator sensor 42 for detecting the accelerator opening a, a brakesensor 43, a vehicle speed sensor 44 for detecting the vehicle speed V,a throttle opening sensor 45 for detecting the throttle opening θrepresenting the acceleration demanded by the driver, a shift positionsensor 46 for detecting the gear shifting range selected by the driver'soperation of a shift lever (not shown) or the like, an oil temperaturesensor 61 for detecting an ATF temperature, an ABS sensor 62 fordetecting a wheel lock/unlock, a vibration gyro sensor 63 for detectingvertical gyro, horizontal gyro or roll angle, a water temperature sensor64 for detecting engine water temperature, a flow rate sensor 65 fordetecting the amount of intake air, an oxygen sensor 66 for detectingoxygen (O₂) concentration, and a kick down switch 67 disposed in anoperating portion of the accelerator pedal (not shown) or the like.Here, the accelerator sensor 42, brake sensor 43, throttle openingsensor 45 and shift position sensor 46 in combination serve as thedriver operation information detection means for detecting parametersrelated to the driver's operation of vehicle.

FIG. 3 shows a front monitor apparatus 48 for monitoring ahead of thevehicle, a line recognition apparatus 49 for recognizing a line markrepresenting a lane of road, a periphery monitor apparatus 50 formonitoring the periphery of the vehicle, a RAM 51 and a ROM 52. Here,the RAM 51 and the ROM 52 in combination serve as the recording means.The gear shifting range can be selected from among neutral range (N),forward range (D), low range (L), reverse range (R) and parking range(P). The front monitor apparatus 48 includes a laser radar, a millimeterwave radar, an ultrasonic sensor or a combination thereof, andcalculates a headway distance La, a headway time Ta, a speed of approachto a preceding vehicle Va, speed Vb of approach to a stop at a point(point of access from a preference road to a non-preference road, arailway crossing, an intersection where a red signal is blinking, or thelike), speed of approach to an obstacle or the like. The peripherymonitor apparatus 50 obtains images ahead of the vehicle by use of acamera such as a CCD, a C-MOS or the like, processes the obtained imagedata, and determines the number of vehicles in the peripheral area,shape of the road ahead, position of a white line, position of the roadshoulder, condition of the road surface, traffic signs, presence of asignal, color of the signal, presence of an obstacle, or the like.

The navigation apparatus 14 has a current position detection section 15for detecting a current position of the vehicle, a data recordingsection 16 with a recording medium in which various items of dataincluding road data have been stored, a navigation processing section 17for performing various routines such as involved in navigationprocessing based on the input information, an input section 34, adisplay section 35, a sound input section 36, a sound output section 37,and a communication section 38.

The current position detection section 15 comprises a GPS 21, ageomagnetic sensor 22, a distance sensor 23, a steering sensor 24, abeacon sensor 25, a gyro sensor 26, an altimeter (not shown), and thelike.

The GPS 21 detects the current ground position of the vehicle byreceiving signals from an artificial satellite, the geomagnetic sensor22 detects the orientation of the vehicle by measuring geomagnetism. Thedistance sensor 23 detects the distance between certain positions on aroad, or the like. As the distance sensor 23, for example, a sensor thatmeasures the rotational speed of an wheel (not shown) for computation ofdistance based on the rotational speed, a sensor that measures theacceleration for computation of distance by integrating twice theacceleration, or the like can be used.

The steering sensor 24 detects a steering angle, and is, for example, anoptical rotation sensor for monitoring rotation of an element rotated bya steering wheel (not shown), a rotation resistance sensor, an anglesensor mounted on the wheel, or the like can be used.

The beacon sensor 25 detects the current position by receiving positioninformation from beacons arranged along a road. The gyro sensor 26detects the turning angle of a vehicle, namely, gyration angle, and cancalculate the orientation in which the vehicle is directed byintegrating the gyration angle. As the gyro sensor 26, for example, agas rate gyro, a vibration gyro, or the like, can be used.

The GPS 21 and beacon sensor 25 can each individually detect the currentposition. The current position can also be detected by combining thedistance detected by the distance sensor 23 with the orientationdetected by the geomagnetic sensor 22 and the gyro sensor 26.Furthermore, the current position can also be detected by combining thedistance detected by the distance sensor 23 with the steering angledetected by the steering sensor 24.

The data recording section 16 is provided with a database comprising amap data file, an intersection data file, a node data file, a road datafile, a picture data file, and a facility information data filecontaining information of facilities in each area such as hotels, gasstations, sightseeing guidance and the like. In the respective datafiles are stored, in addition to data for searching for the route,various data for displaying a guidance view along the searched route, apicture, frame view, or the like to show features of the intersection orroute, distance to the next intersection, direction of travel at thenext intersection or the like, displaying other guidance information ona screen (not shown) of the display section 35. Here, in the datarecording section 16, various data for outputting appropriateinformation by a sound output section 37 is also stored.

In the intersection data file, intersection data concerningintersections is stored, while node data concerning node points isstored in the node data file, and road data concerning roads is storedin the road data file, respectively. The road condition is representedby the intersection data, node data and road data. Here, the node dataconstitutes at least the position and shape of a road represented by mapdata stored in the map data file, and is composed of data representingthe branching points (including intersections, T-junctions, or thelike), node points, and links connecting node points of an actual road.Here, the node point indicates at least the position of bends in a road,and the branching point and node point are represented at least by thelatitude, longitude and altitude.

The road data includes width, inclination, cant, bank, road surfacecondition, number of lanes, spot where the number of lanes is reduced,spot where the road narrows, and other elements constitute a roaditself; radius of curvature, intersection, T-junction, entrance to acorner, and other elements constitute corner data; railway crossing,speedway exit ramp, toll gate of a speedway, road category (nationalroad, ordinary road, speedway or the like), urban road, mountain road,uphill road, downhill road, congested road and other elements constituteroad attribute data.

The navigation processing section 17 comprises a CPU 31 for controllingthe entire navigation apparatus 14, a RAM 32 used as a working memorywhen the CPU 31 performs various calculations, and a ROM 33 serving as arecording medium containing various programs for performing the searchof route to the destination, travel guidance in route, decision ofspecific section, or the like, in addition to the control program. Theinput section 34, display section 35, sound input section 36, soundoutput section 37 and communication section 38 are connected to thenavigation processing section 17.

The data recording section 16 and the ROM 33 comprise a magnetic core(not shown), semiconductor memory, or the like. Moreover, for the datarecording section 16 and the ROM 33, various recording media such as amagnetic tape, magnetic disk, floppy disk, magnetic drum, CD, MD, DvD,optical disk, IC card, and optical card may also be used.

In this embodiment, various programs are stored in the ROM 33 andvarious data are stored in the data recording section 16. However, theprograms and data may also be stored in a common external recordingmedium. In this case, for example, a flash memory may be provided in thenavigation processing section 17, and the programs and data may be readout from the external recording medium and written into the flashmemory. Therefore, the programs and data can be updated by changing theexternal recording medium. In addition, the control program and the likeof the automatic transmission control section 12 can also be stored inthe external recording medium. Thus, programs stored in variousrecording media can be started to perform various routines based on thedata.

The communication section 38 is designed to transmit and receive variousdata through an FM transmission apparatus, a telephone line, or thelike, and receives various data including road information such ascongestion, traffic accident, D-GPS information for determiningdetection error of the GPS 21, or the like.

The input section 34 is designed to correct the current position whenthe travel starts, or input the destination. A keyboard, mouse, bar codereader, light pen, remote control apparatus for remote operation, or thelike, arranged separately from the display section 35 can be used as theinput section 34. Moreover, the input section 34 may comprise a touchpanel for inputting by touching a key or menu shown as an image on thescreen of the display section 35.

Operation guidance, operation menu, guidance for operation keys, routeto the destination, guidance along the route to be traveled and the likeare displayed on the screen of the display section 35. A CRT display,liquid crystal display, plasma display, hologram apparatus forprojecting a hologram on the front glass or the like can be used as thedisplay section 35.

The sound input section 36 comprises a microphone (not shown), and caninput necessary information by means of sound. In addition, the soundoutput section 37 comprises a sound synthesis apparatus (not shown) anda speaker, and outputs sound information, for example, guidanceinformation, gear shifting information synthesized by the soundsynthesis apparatus from the speaker, to inform the driver. Here, exceptfor sound synthesized by the sound synthesis apparatus, various soundsand various guidance information stored in a recording medium such as atape memory can be output from the speaker.

In the navigation apparatus 14 thus structured, display processing means(not shown) of the CPU 31 opens a guidance screen on the screen of thedisplay section 35 by executing the display routine to show the currentposition and a map of the periphery on the guidance screen. Then, whenthe destination is set by the driver's operation of the input section34, a route search processing means (not shown) of the CPU 31 searchesfor the route from the current position to the destination by executingthe route search routine. Then, when the route is retrieved, the displayprocessing means opens the guidance screen by executing the displayroutine, shows the current position, the map of the periphery and thesearched route on the guidance screen. Then, the route guidance isstarted whereby the driver can travel according to the route guidance.

The automatic transmission control section 12 reads, as travelenvironment, vehicle information and operation information from thevehicle/driver operation information detection section 40, navigationinformation from the navigation processing section 17, and vehicleenvironment information from the front monitor apparatus 48 and theperiphery monitor apparatus 50. Moreover, the automatic transmissioncontrol section 12 reads vehicle periphery information, environmentinformation and display information as necessary for control of thecontinuously variable transmission 10. Travel environment detectionmeans 91 (FIG. 1) is composed of the vehicle/driver operationinformation detection section 40, navigation processing section 17,front monitor apparatus 48, line recognition apparatus 49, and peripherymonitor apparatus 50.

As the vehicle information, vehicle speed V detected by the vehiclespeed sensor 44, engine throttle opening θ detected by the throttleopening sensor 45, engine speed N_(E) detected by the engine speedsensor 165, engine speed variation calculated based on the engine speedN_(E), vehicle speed variation (acceleration and deceleration)calculated based on the vehicle speed V, ATF temperature detected by theoil temperature sensor 61, wheel lock/unlock detected by the ABS sensor62, vertical gyro, horizontal gyro or roll angle detected by thevibration gyro 63, engine water temperature detected by the watertemperature sensor 64, intake air amount detected by the flow ratesensor 65, oxygen concentration detected by the oxygen sensor 66, andthe like, can be used.

The operation information may include accelerator opening α detected bythe accelerator sensor 42, speed of depression Ve of the acceleratorpedal calculated based on the accelerator opening α or kick down on/offinformation, kick down on/off information detected by the kick downswitch 67, brake on/off information detected by a brake switch (notshown), force or speed of depression of a brake pedal (not shown)detected by the brake sensor 43, force or speed of depression of thebrake pedal detected by a brake hydraulic pressure sensor (not shown),steering angle detected by the steering sensor 24 or a steering speedcalculated based on the steering angle, turn signal off, right turnsignal on or left turn signal on detected by the turn signal sensor 41,power (sport) mode, normal (economy) mode, snow (hold) mode or auto modedetected by mode switch (not shown), wiper off, intermittent on,continuous (low) on or continuous (high) on detected by a wiper switch(not shown), small light on, head light (low) on, head light (high) onor auto on detected by a light switch (not shown), a gear shifting rangedetected by an N. S. switch (not shown) and the like can be used.

The navigation information may include shape of a road, road attribute,number of lanes, intersection type, town information or area informationstored in the data recording section 16, time (season) detected by theGPS 21, VICS congestion level obtained by the communication section 38,D-GPS information or traffic congestion information obtained by FMmultiplex broadcasting, map information obtained by satellite signals,map information, traffic congestion information, leisure information orweather information obtained by a cellular phone (not shown), ETCinformation, toll fare information, map information, intersectioninformation or town information obtained by a DSRC (not shown),inter-vehicle information detected by the SS radio, and the like.

The vehicle environment information may include headway distance La,headway time Ta, travel lane where preceding vehicle is traveling orobstacle detected by the front monitor apparatus 48, and number ofvehicles in the periphery, shape of a road ahead, white line position,road shoulder position, condition of a road surface, road signs,presence of a signal, color of the signal, presence of an obstacle andthe like detected the periphery monitor apparatus 50, and the like.

The vehicle periphery information may include an obstacle detected by anultrasonic sensor (not shown), an obstacle detected by a microwavesensor (not shown), an obstacle detected by a camera (not shown), andthe like.

The environment information may include outside temperature detected byan outside temperature sensor (not shown), solar radiation detected by asolar radiation sensor (not shown) and the like.

Further, as the display information, color of the signal detected by thebeacon sensor 25 may also be used.

Next, the operation of the automatic transmission control apparatus willbe described with reference to FIGS. 4-9. In FIG. 5 to FIG. 9, theabscissa represents the vehicle speed V, and the ordinate represents theengine speed N_(E).

First, the automatic transmission control section 12 (FIG. 3) judges thecontrol mode selected by the driver. That is, it is judged whether thenormal control mode or the adaptive control mode is selected by thedriver's operation of a mode selection switch (not shown). When thenormal control mode is selected, normal control processing means of theautomatic transmission control section 12 performs the normal controlprocessing, that is, reads, as shift control information, the selectedgear shifting range, vehicle speed V, throttle opening a and enginespeed N_(E), refers to the gear shifting diagram shown in FIG. 5 storedin the ROM 52, sets the shift schedule corresponding to the gearshifting diagram, and calculates a target value for engine speed N_(E),that is, target engine speed N_(E)* based on the vehicle speed V andthrottle opening θ in the selected gear shifting range.

Next, the normal control processing means compares the engine speedN_(E) with the target engine speed N_(E)*, generates a gear shift signalbased on the results of comparison, and outputs a suitable gear ratio.Then, when the engine speed N_(E) is higher than the target engine speedN_(E)*, an up-shift is performed to the appropriate gear ratio, when theengine speed N_(E) is equal to the target engine speed N_(E)*, no gearshifting is performed, and when the engine speed N_(E) is lower than thetarget engine speed N_(E)*, a down-shift to the appropriate gear ratiois executed.

In the gear shifting diagram shown in FIG. 5, the gear shifting regionAR1, which is defined by a line L1 representing the maximum gear ratio,a line L2 representing the minimum gear ratio, a line L3 representingthe maximum engine speed N_(E), or, maximum service speed when thethrottle opening θ is 100%, a line L4 representing the minimum enginespeed N_(E) or, minimum service speed when the throttle opening θ is 0%,and a line L5 representing the limit value of the vehicle speed V, isset.

Therefore, when the driver depresses the accelerator pedal (not shown),the vehicle speed V and the engine speed N_(E) change from the zeropoint along the line L1 according to the increase of the throttleopening θ. Then, as the driver continues to depress the acceleratorpedal by a constant amount, the vehicle speed V increases from the lineL1 toward the line L2 with the degree of the throttle opening θ keptconstant. Meanwhile, the gear ratio lowers gradually. Then, when thevehicle speed V attains a value on line L2, a stationary state isestablished, and the vehicle is made to travel at the intended vehiclespeed V and engine speed N_(E).

When the driver releases the accelerator pedal from the stationarystate, the vehicle speed V and the engine speed N_(E) change along theline L2 according to the decrease of the throttle opening θ, and thenthe vehicle speed V changes along the line L4 until the throttle openingθ becomes 0%. Meanwhile, the gear ratio increases gradually. Then, whenthe vehicle speed V attains a value on the line L1, the vehicle speed Vand the engine speed N_(E) thereafter change along the line L1, beforeattaining the zero point.

On the other hand, when the adaptive control mode is selected, adaptivecontrol processing means (not shown) of the automatic transmissioncontrol section 12 executes the adaptive control routine, that is,selecting a gear shifting diagram based on a predetermined controllogic, corresponding to the travel environment stored in the ROM 52, andsetting a shift schedule based on the gear shifting diagram.

The adaptive control processing means reads the travel environmentdetected by the travel environment detection means 91 (FIG. 1). Then,the travel area judgment means of the adaptive control processing meansjudges the area where the vehicle travels based on the travelenvironment, that is, the travel area. In this embodiment, the roadattribute is read as the travel environment, and it is judged whetherthe travel area is, based on the road attribute, an urban road, acongested road, a suburban road, a mountain road, an uphill road, anexpressway, or the like.

Then, the shift schedule setting processing means of the adaptivecontrol processing means selects a gear shifting diagram correspondingto the judged travel area, refers to the selected gear shifting diagram,and sets the shift schedule based on the gear shifting diagram.

The shift schedule setting processing means selects: for example, afirst gear shifting diagram M1 shown in FIG. 6 in the case where thetravel area is an urban road or a congested road; a second gear shiftingdiagram M2 shown in FIG. 7 in the case where the travel area is asuburban road; a third gear shifting diagram M3 shown in FIG. 8 in thecase where that the travel area is a mountain road or an uphill road;and a fourth gear shifting diagram M4 shown in FIG. 9 in the case wherethe travel area is an expressway.

The first gear shifting diagram M1 is appropriate for making the vehicletravel at a medium speed or low speed. Here, a gear shifting region AR11bounded by the lines L11 to L14 is set so that the engine speed N_(E) isin a low speed region, the engine speed N_(E) is set lower than thelines L3, L4, respectively, for the line L13 representing the maximumservice speed and the line L14 representing the minimum service speedand, at the same time, the lower the vehicle speed V is for the line 14,the lower the engine speed N_(E) becomes.

The second gear shifting diagram M2 is appropriate for making thevehicle travel at a medium speed or high speed. Here, a gear shiftingregion AR12 is set as defined by a line L15 for restricting the gearratio from increasing when the vehicle speed V becomes equal to or morethan a suitable value, in addition to the line L11 representing themaximum gear ratio, L12 representing the minimum gear ratio, and thelines L13, L14. In this case, the vehicle can be made to travel byreducing the gear ratio at a medium speed of 50 km/h or more notincluding 80 km/h.

The third gear shifting diagram M3 is appropriate for vehicle travelwith a large gear ratio and driving force. Here, a gear shifting regionAR13 defined by the lines L11 to L14 is set, and the gear ratio of theline L12 is made higher than the theoretical minimum gear ratio of theline L2. As a result, the gear ratio is prohibited from being lowered,and the maximum gear ratio can be achieved even at 50 km/h.

The fourth gear shifting diagram M4 is appropriate for vehicle travel ata high speed. Here, a gear shifting region AR14 is set, which region isdefined by the line L15, and a line L16 for inhibiting the vehicle speedfrom becoming equal to or more than a suitable value, in addition to thelines L11 to L14. In this case, since the maximum gear ratio can beachieved at 80 km/h or more, the engine speed N_(E) is inhibited fromincreasing, and noise generation is prevented.

In the continuously variable transmission 10 (FIG. 2), when the pinchingpressure for the belt 132 is high, the torque transmission efficiencybecomes low. However, if the pinching pressure for the belt 132 isreduced, the transmission torque may vary and exceed a suitable torquewhen the vehicle is bumped due to a rough road, or when the acceleratorpedal is depressed suddenly. As a result, slippage would occur betweenthe primary pulley 126 or the secondary pulley 131 and the belt 132, andthus the primary pulley 126, the secondary pulley 131 and the belt 132would see increased wear, remarkably lowering the durability of thecontinuously variable transmission 10.

Therefore, generally, as mentioned above, by setting a suitableallowance m to:

m=(a−1)×T ₁

based on the input torque T₁ and the constant a (=1.4), and increasingthe pinching pressure by the allowance m, slippage is prevented.

The allowance m may also be set, as necessary, to:

m=(a−1)×T ₁ +b

Here, b is a constant. Otherwise, the allowance m corresponding to thevehicle speed V, input torque T₁, input pulley revolution speed and thelike may be calculated beforehand, and the calculated allowance may bemapped and stored in the ROM 52.

However, if the pinching pressure is constantly higher by the allowancem, the torque transmission efficiency is decreased accordingly. Thus,allowance correction processing means (not shown) of the automatictransmission control section 12 makes an allowance correction, and thetorque variation estimation processing means 92 of the allowancecorrection processing means estimates transmission torque variationduring travel based on the detected travel environment. Here, thepinching pressure change processing means 93 of the allowance correctionprocessing means corrects the allowance m, and changes the pinchingpressure based on the result of estimation by the torque variationestimation processing means 92.

Next, the flowchart shown in FIG. 4 will be described.

Step S1: It is judged whether the normal control mode has been selected,or the adaptive control mode has been selected by the driver. In thecase that the normal control mode has been selected, the routineproceeds to step S2 and in the case that the adaptive control mode hasbeen selected, the routine proceeds to step S3.

Step S2: The normal control subroutine is executed, and the processingis terminated.

Step S3: The adaptive control subroutine is executed.

Step S4: The allowance correction subroutine is executed, and theprocessing is terminated.

Next, a subroutine for the allowance correction in step S4 in FIG. 4will be described with reference to FIGS. 10 and 11.

The torque variation estimation processing means 92 (FIG. 1) judgeswhether or not the vehicle is traveling forward, and if travelingforward, estimates whether or not the transmission torque will tend tovary easily during travel based on the shift schedule set in the shiftschedule setting processing, and how much it will vary if it finds thatthe transmission torque will tend to vary easily. Then the pinchingpressure change processing means 93 corrects the allowance m and changesthe pinching pressure for the belt 132 based on the estimation made bythe torque variation estimation processing means 92. That is, thepinching pressure is increased when the transmission torque tends tovary easily, and the pinching pressure is decreased when thetransmission torque hardly varies. Therefore, the correction value ofthe allowance m is set with variation of hydraulic pressure supplied tothe hydraulic servos 133, 135, variation of engine torque, variation ofthe performance of the torque converter 106, reaction force received bythe wheel from the road surface, margin for inhibiting the engine torquefrom varying when the accelerator pedal depression amount changessuddenly, and the like, taken into account.

For instance, in the case where the gear shifting diagram selected bythe shift schedule setting processing is the first gear shifting diagramM1, it is estimated that the transmission torque hardly varies duringtravel, the allowance m is corrected by a correction value δ1 and isreduced to m−δ1; in the case where the selected gear shifting diagram isthe second gear shifting diagram M2, it is estimated that thetransmission torque hardly varies during travel, and the allowance m isnot corrected; in the case where the selected gear shifting diagram isthe third gear shifting diagram M3, it is estimated that thetransmission torque will tend to vary easily during travel, theallowance m is corrected by a correction value δ2 and is increased tom+δ2; and in the case where the selected gear shifting diagram is thegear shifting diagram M4, it is estimated that the transmission torquewill hardly vary, the allowance m is corrected by a correction value δ3and is reduces to m−δ3.

The correction values δ1 to δ3 are set previously in accordance with thedegree of the transmission torque variation. In this embodiment, thegear shifting diagram is selected based on the judgment whether thetravel area is an urban road, a congested road, a suburban road, amountain road, an uphill road, an expressway or the like. Therefore, thecorrection values δ1 to δ3 are set by estimating how the transmissiontorque will vary in the respective travel areas. The situations wherethe transmission torque will vary by travel area include: immediatelyafter the change from the deceleration state to the acceleration state;immediately after the change from the acceleration state to thedeceleration state; when the steering wheel is turned while theaccelerator pedal (not shown) is depressed while passing a precedingvehicle on an expressway; when the steering wheel is turned afterdepressing the accelerator pedal for acceleration after the vehicle hasrounded a curve on a snaking road; and when the accelerator pedal isdepressed after the brake pedal is released.

Thus, the pinching pressure is prevented from constantly increasingbecause the transmission torque variation during travel is estimated tovary the allowance m, i.e., the allowance m is increased when thetransmission torque tends to vary easily and the pinching pressure isthereby increased, and the allowance m is decreased when thetransmission torque hardly varies and the pinching pressure is therebylowered. Accordingly, the torque transmission efficiency can beincreased, and the fuel efficiency can thus be improved.

Moreover, because pinching pressure is adjusted in accordance with thetravel environment, slippage is prevented from occurring between theprimary pulley 126 or the secondary pulley 131 and the belt 132.Consequently, wear of the primary pulley 126, the secondary pulley 131and the belt 132 is reduced and the durability of the continuouslyvariable transmission 10 (FIG. 2) is improved.

Next, the flowchart of FIG. 10 will be described.

Step S4-1: It is judged whether or not the vehicle is traveling forward.If the vehicle is traveling forward, the subroutine proceeds to stepS4-2, and if the vehicle is not traveling forward, the subroutinereturns to the start.

Step S4-2: The allowance m is corrected according to the shift schedule,and the subroutine returns to the start.

A second embodiment of the invention will now be described withreference to FIG. 12. In the second embodiment, a normal controlprocessing means (not shown) of the automatic transmission controlsection 12 (FIG. 3) performs a normal control processing similar to thefirst embodiment. Then, allowance correction processing means (notshown) of the automatic transmission control section 12 executes anallowance correction subroutine, estimates, based on the travelenvironment, whether or not the transmission torque will tend to varyeasily during travel, and how much it will vary in the case where itfinds that the transmission torque tends to vary easily and corrects theallowance m based on these estimations.

Next, the flowchart of FIG. 12 will be described.

Step S11: The normal control subroutine is executed.

Step S12: The allowance correction subroutine is executed, and theroutine of FIG. 12 is terminated.

Next, the subroutine for the allowance correction, i.e, step S12 in FIG.12, will be described with reference to FIGS. 13 and 14.

The torque variation estimation processing means 92 (FIG. 1) of theallowance correction processing means judges whether or not the vehicleis traveling forward, then if traveling forward, reads navigationinformation as travel environment and judges the travel area based onthe navigation information. In this case, as travel area, it is judgedwhether it is an urban road, a congested road, a mountain road, anuphill road, a downhill road, an expressway, or the like.

Then, the torque variation estimation processing means 92 estimateswhether or not the transmission torque will tend to vary easily duringtravel based on the travel area, and how much it will vary in the casewhere it finds that the transmission torque tends to vary easily. Thepinching pressure change processing means 93 of the allowance correctionprocessing means corrects the allowance m based on the estimation madeby the torque variation estimation processing means 92, and changes thepinching pressure accordingly.

For instance, when the travel area is judged to be an urban road, it isestimated that the transmission torque will hardly vary during travel,and the allowance m is not corrected. When the travel area is judged tobe a congested road, it is estimated that there is only a smallpossibility of a sudden change in the degree to which the acceleratorpedal is depressed, for example, so that the transmission torque willhardly vary during travel. As a result, the allowance m is corrected bya correction value δ11 and reduced to m−δ11. When the travel area isjudged to be a mountain road, it is estimated that the degree ofaccelerator pedal depression will be medium to high, that is, the degreeof throttle opening will be medium to high, so that the acceleratorpedal will be depressed and released frequently, and the transmissiontorque will tend to vary easily during travel. As a result, theallowance m is corrected by a correction value δ12 and increased tom+δ12. When the travel area is judged to be an uphill road, it isestimated that degree of the throttle opening will be medium to high, sothat the accelerator pedal will be depressed and released frequently,and the transmission torque will tend to vary easily during travel. As aresult, the allowance m is corrected by a correction value δ13 andincreased to m+δ13. When the travel area is judged to be a downhillroad, it is estimated that there is only a small possibility of a suddenchange in degree of depression of the accelerator pedal, for example,and that the transmission torque will hardly vary during travel. As aresult, the allowance m is corrected by a correction value δ14 andreduced to m−δ14. When the travel area is judged to be an expressway, itis estimated that there will be only a small possibility of a suddenchange in the degree of depression of the accelerator pedal, forexample, and that transmission torque will hardly vary during travel. Asa result, the allowance m is corrected by a correction value δ15 andreduced to m−δ15. The correction values δ11 to δ15 are set previouslyaccording to the degree of the transmission torque variation.

Next, the flowchart of FIG. 13 will be described for the secondembodiment.

Step S12-1: It is judged whether or not the vehicle is travelingforward. If the vehicle is traveling forward, the subroutine proceeds tostep S12-2, and when the vehicle is not traveling forward, thesubroutine returns to the start.

Step S12-2: The travel area is judged based on the navigationinformation.

Step S12-3: The allowance m is corrected according to the travel area,and the subroutine returns to the start.

A third embodiment of the invention will now be described with referenceto FIGS. 15 and 16.

The torque variation estimation processing means 92 (FIG. 1) of theallowance correction processing means judges whether or not the vehicleis traveling forward, and if traveling forward, reads navigationinformation and vehicle environment information as travel environment,and judges at least either the travel area based on the navigationinformation or environment information. In judging the travel area, itis judged whether the travel area is an expressway, an urban road, orthe like. In judging the driving state, it is determined that there isno vehicle ahead (no vehicle ahead), that there is a vehicle ahead(vehicle ahead), or that, during a stop, there is a vehicle ahead(vehicle ahead during a stop), or the like, based on the lane forproceeding forward. When only the travel area is to be judged, onlynavigation information is read, and when only the driving state is to bejudged, only the vehicle environment information is read.

Then, the torque variation estimation processing means 92 estimateswhether or not the transmission torque tends to vary easily duringtravel based on at least either the travel area or the driving state,and how much it will vary in the case where the transmission torque isfound to tend to vary easily. The pinching pressure change processingmeans 93 of the allowance correction processing means corrects theallowance m based on the estimation made by the torque variationestimation processing means 92, and changes the pinching pressureaccordingly.

For example, when it is judged that the vehicle travels on anexpressway, and there is no vehicle ahead, it is estimated that thevehicle will travel mostly at a constant vehicle speed V, and there isonly a small possibility of sudden acceleration, so that thetransmission torque will hardly vary during travel. As a result, theallowance m is corrected by a correction value δ21 and reduced to m−δ21.When it is judged that the vehicle travels on an expressway and there isa vehicle ahead, it is estimated that there is a large possibility ofsudden acceleration for passing the preceding vehicle, so that thetransmission torque will tend to vary easily during travel. As a result,the allowance m is corrected by a correction value δ22 and increased tom+δ22. When it is judged that the vehicle travels on an urban road, itis estimated that the transmission torque will hardly vary duringtravel. As a result, the allowance m is not corrected. When it is judgedthat there is a vehicle ahead during a stop, it is estimated that thereis only a small possibility of sudden take-off, so that the transmissiontorque will hardly vary during travel. As a result, the allowance m iscorrected by a correction value δ23 and reduced to m+δ23. The correctionvalues δ21 to δ23 are preset according to the degree of the transmissiontorque variation.

Next, the flowchart of FIG. 15 will be described.

Step S12-11: It is judged whether or not the vehicle is travelingforward. If the vehicle is traveling forward, the subroutine proceeds tostep S12-12, and if the vehicle is not traveling forward, the subroutinereturns to the start.

Step S12-12: At least either the travel area is judged based on thenavigation information or the driving state is judged based on thevehicle environment information.

Step S12-13: The allowance m is corrected according to at least eitherthe travel area or the driving state, and the subroutine returns to thestart.

Next, a fourth embodiment of the invention will be described.

FIG. 17 shows a subroutine for the allowance correction in the fourthembodiment of the invention, and FIG. 18 shows a table of correctionvalues used in the fourth embodiment of the invention.

The torque variation estimation processing means 92 (FIG. 1) of theallowance correction processing means judges whether or not the vehicleis traveling forward, and if traveling forward, reads as travelenvironment the state of road surface from the vehicle environmentinformation, and judges the road surface condition based on the state ofroad surface. In this case, the road surface is judged to be an asphaltroad surface, a concrete road surface, a gravel road surface (gravelroad), an ice and snow covered road surface (snow covered road or snowand ice mixture covered road), a smoothly frozen road surface, or thelike. Since the state of road surface is also recorded as road data inthe current position detection section 15 (FIG. 3), the road surfacecondition may be judged by reading the navigation information.

Then, the torque variation estimation processing means 92 estimateswhether or not the transmission torque will tend to vary easily duringtravel based on the road surface condition, and how much it will vary inthe case where the transmission torque will tend to vary easily. Thepinching pressure change processing means 93 of the allowance correctionprocessing means corrects the allowance m based on the estimation madeby the torque variation estimation processing means 92, and changes thepinching pressure accordingly.

For example, when the road surface condition is judged to be an asphaltroad surface or a concrete road surface, it is estimated that thetransmission torque will hardly vary during travel. As a result, theallowance m is not corrected. When the road surface condition is judgedto be a gravel road surface, it is estimated that the wheel will receiveresistance when riding on the gravel and that the reaction forcereceived from the road surface will be large, so that the transmissiontorque will tend to vary easily during travel. As a result, theallowance m is corrected by a correction value δ31 and increased tom+δ31. When the road surface condition is judged to be an ice and snowcovered road surface, it is estimated that the wheel will receiveresistance when riding over accumulated snow and that the reaction forcereceived from the road surface will be large, so that the transmissiontorque will tend to vary easily during travel. As a result, theallowance m is corrected by a correction value δ32 and increased tom+δ32. When the road surface condition is judged to be a smoothly frozenroad surface, it is estimated that the coefficient of friction of theroad surface is small, that the torque which can be transmitted by thedrive wheels will be small, and that the reaction force received fromthe road surface will be small, so that the transmission torque willhardly vary during travel. As a result, the allowance m is corrected bya correction value δ33 and reduced to m−δ33. The correction values δ31to δ33 are preset for the degree of the transmission torque variation.

Next, the flowchart of FIG. 17 will be described.

Step S12-21: It is judged whether or not the vehicle is travelingforward. If the vehicle is traveling forward, the subroutine proceeds tostep S12-22, and if the vehicle is not traveling forward, the subroutinereturns to the start.

Step S12-22: The road surface condition is judged based on the vehicleenvironment information.

Step S12-23: The allowance m is corrected according to the travel area,and the subroutine returns to the start.

The invention is not limited to the aforementioned embodiments, but canbe variously modified within the spirit of the invention, and suchmodified embodiments are not excluded from the scope of the invention.

What is claimed is:
 1. An automatic transmission control apparatus for avehicle comprising: a primary pulley; a secondary pulley; a beltstretched around the primary pulley and the secondary pulley; travelenvironment determination means for determining at least one parameterrelated to travel environment of the vehicle; torque variationestimation means for estimating variation in transmission torque duringtravel, based on the determined travel environment; transmission controlmeans for generating a shift signal; primary pulley regulating means forregulating said primary pulley so as to change effective diameters ofthe primary and secondary pulleys, responsive to the shift signal;pinching pressure change processing means for determining a pinchingpressure in accordance with the estimated variation in transmissiontorque; and pinching pressure regulating means for regulating saidsecondary pulley to change pinching pressure exerted on said belt bysaid secondary pulley in accordance with the determined pinchingpressure.
 2. The automatic transmission control apparatus according toclaim 1 wherein said pinching pressure change processing meansdetermines a pinching pressure including an allowance m and changes saidallowance m in accordance with the estimated variation in transmissiontorque.
 3. The automatic transmission control apparatus according toclaim 2 wherein said transmission control means refers to a gearshifting diagram stored in memory, applies a selecting shifting range, adetected vehicle speed, a detected throttle opening and a detectedengine speed to the gear shifting diagram to determine a target enginespeed and generates the shift signal in accordance with the determinedtarget engine speed.
 4. The automatic transmission control apparatusaccording to claim 3 wherein said transmission control means has anadaptive control mode wherein said transmission control means selectsone of plural gear shifting diagrams in accordance with the estimatedvariation in transmission torque.
 5. The automatic transmission controlapparatus according to claim 4 wherein a different correction factor isassigned to each of the plural gear shifting diagrams, and wherein saidpinching pressure change processing means changes said allowance m bysaid correction factor.
 6. The automatic transmission control apparatusaccording to claim 5 wherein said transmission control means also has anormal control mode wherein said transmission control means selects agear shifting diagram independent of the estimated variation intransmission torque.
 7. The automatic transmission control apparatusaccording to claim 1, wherein the pinching pressure change processingmeans increases the determined pinching pressure when the torquevariation estimation means estimates that transmission torque will tendto vary easily and lowers the determined pinching pressure when thetorque variation estimation means estimates that the transmission torquewill tend to hardly vary.
 8. The automatic transmission controlapparatus according to claim 7, wherein the torque variation estimationprocessing means estimates that the transmission torque will hardly varyin a travel environment where it is estimated that a sudden change ofthrottle opening will not occur.
 9. The automatic transmission controlapparatus according to claim 7, wherein the torque variation estimationprocessing means estimates that the transmission torque will tend tovary easily in a travel environment where it is estimated that a degreeof throttle opening will be medium to high, and that the acceleratorpedal will be engaged and released frequently.
 10. The automatictransmission control apparatus according to claim 7, wherein the torquevariation estimation processing means estimates that the transmissiontorque will hardly vary in a travel environment where it is estimatedthat there is a low probability of sudden acceleration and that thetransmission torque will tend to vary easily in a travel environmentwhere it is estimated that there is a high probability of suddenacceleration.
 11. The automatic transmission control apparatus accordingto claim 7, wherein the torque variation estimation processing meansestimates that the transmission torque will tend to vary easily in atravel environment where it is estimated that the reaction forcereceived from a road surface will be large and that the transmissiontorque will tend to hardly vary in a travel environment wherein it isestimated that the reaction force received from a road surface will besmall.
 12. The automatic transmission control apparatus according toclaim 10, wherein the torque variation estimation processing meansestimates that there is a low probability of sudden acceleration whenthere is no vehicle ahead during travel on an expressway and that thereis a high probability of sudden acceleration when there is a vehicleahead during travel on an expressway.
 13. The automatic transmissioncontrol apparatus according to claim 10, wherein the torque variationestimation processing means estimates that there is a low probability ofsudden acceleration when there is a vehicle ahead during a stop.
 14. Theautomatic transmission control apparatus according to claim 8, whereinthe at least one parameter is an expressway.
 15. The automatictransmission control apparatus according to claim 11, wherein it isestimated that the reaction force received from a road surface will belarge when the road surface is a gravel road surface.
 16. The automatictransmission control apparatus according to claim 11, wherein it isestimated that the reaction force received from a road surface will belarge when the road surface is an ice and/or snow covered road surface.17. The automatic transmission control apparatus according to claim 11,wherein it is estimated that the reaction force received from a roadsurface will be small when the road surface is a smoothly frozen roadsurface.
 18. The automatic transmission control apparatus according toclaim 1, wherein the torque variation estimation processing meansestimates the transmission torque variation in accordance with selectionof a shift schedule based on the determined travel environment.
 19. Theautomatic transmission control apparatus according to claim 1, whereinthe at least one parameter is a travel area.
 20. The automatictransmission control apparatus according to claim 1, wherein the atleast one parameter is road congestion.
 21. The automatic transmissioncontrol apparatus according to claim 1, wherein the at least oneparameter is a downhill slope.
 22. The automatic transmission controlapparatus according to claim 1, wherein the at least one parameter istravel area and/or driving state.
 23. The automatic transmission controlapparatus according to claim 1, wherein the at least one parameter is amountain road.
 24. The automatic transmission control apparatusaccording to claim 1, wherein the at least one parameter is an uphillslope.
 25. The automatic transmission control apparatus according toclaim 1, wherein the at least one parameter is road surface condition.26. The automatic transmission control apparatus according to claim 1,wherein the travel environment determination means determines the atleast one parameter is based on information pertaining to operation ofthe vehicle.
 27. The automatic transmission control apparatus accordingto claim 1 wherein said pulleys each comprise a movable sheave, whereinsaid primary pulley regulating means regulates said primary pulley bymovement of the movable sheave of the primary pulley and said pinchingpressure regulating means regulates said secondary pulley by movement ofthe movable sheave of said secondary pulley.
 28. The automatictransmission control apparatus according to claim 27 wherein saidprimary pulley regulating means and pinching pressure regulating meansare hydraulic actuators comprising the movable sheaves, serving aspistons, moved axially responsive to hydraulic pressure.
 29. Theautomatic transmission control apparatus according to claim 1 whereinsaid pinching pressure regulating means regulates said second pulleywhen the transfer of rotation is from the engine to the primary pulley.30. An automatic transmission control method for controlling atransmission apparatus mounted in a vehicle and comprising primary andsecondary pulleys and a belt stretched around the pulleys, said controlmethod comprising: determining at least one parameter related to travelenvironment of the vehicle; estimating variation in transmission torqueduring travel, based on the determined travel environment; generating ashift signal; regulating the primary pulley so as to change effectivediameters of the pulleys, responsive to the shift signal; determining apinching pressure in accordance with the estimated variation intransmission torque; and regulating the secondary pulley to change thepinching pressure exerted on the belt by the secondary pulley inaccordance with the determined pinching pressure.
 31. The automatictransmission control method according to claim 30 wherein the secondarypulley is regulated to change the pinching pressure when the transfer ofrotation is from the engine to the primary pulley.
 32. Amachine-readable medium having encoded thereon a program for executionof the transmission control method of claim 30.